Hunting for dark matter with GPS and atomic clocks

Atomic clocks are arguably the most accurate scientific instruments ever build. Modern clocks are astonishing timepieces guaranteed~to~keep time within a second over the age of the Universe.~~Attaining this accuracy requires that the quantum oscillator be well protected from environmental noise and that clock perturbations be well controlled and characterized. This opens intriguing prospects of using clocks to study subtle effects, and it is natural to ask if such accuracy can be harnessed for dark matter searches. The cosmological applications of atomic clocks so far have been limited to searches of the uniform-in-time drift of fundamental constants. We point out that a transient in time change of fundamental constants can be induced by dark matter objects that have large spatial extent, and are built from light non-Standard Model fields. A correlated network~of atomic clocks, such as atomic clocks onboard satellites of the GPS constellation, can be used as a tool to search for ``clumpy'' dark matter. I will present initial results of our dark matter search with archival GPS data.